Start with one .015" (pink) shim for 9mm and .40 cal; and one .004" (tan) shim for .357 sig and 45 acp. Amount of needed shim will vary, depending on load and particular barrel. Approximately, each increment of .002" to .0025" of elevation shim will affect bullet impact by 1" at 25 yards. With the tools provided with each sight kit, most will be able to install our Glock sights without professional help.